Is it permissible for a Muslim to begin and end his fasting of Ramadhaan according to the timings of a country other than the one in which he is living?

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.

The rule is that a Muslim depends, in his fasting and in breaking his fast, on sighting the moon in the country in which he lives provided that this country depends upon the Sharee’ah-approved sighting and not astronomical calculations. The Messenger of Allaah, sallallaahu ‘alayhi wa sallam, said: "Fasting is the day when you (collectively) fast, breaking fast is the day when you (collectively) break your fast and sacrifice is the day when you (collectively) offer your sacrifice…" [At-Tirmithi] Abu ‘Eesa (At-Tirmithi) said, "This Hadeeth is Hasan. It was interpreted by some scholars to mean that fasting and breaking fast should be with the main group and the majority of people." Shaykh Al-Albaani classified this narration as  Saheeh.

Therefore, it is impermissible for a Muslim to fast and break his fast depending on the sighting that takes place outside his country. This holds true if it (the country in which he lives) depends, in determining the beginning of the new month, on the Sharee’ah-approved way of sighting such as assigning an upright and knowledgeable group to search for the new moon and find it using Sharee’ah-approved means.  

Allaah Knows best.